The Children's Hospital of Philadelphia (CHOP) is a primary treatment center for children with malignant diseases. As a member institution of Children's Cancer Study Group A (CCSGA) the study and treatment of these diseases will be pursued via the protocols of CCSGA. Chemotherapy, and possibly immunotherapy, will be used alone or in conjunction with surgery and/or radiation therapy, according to the dictates of the protocols, to try to determine less toxic and more effective means of improving survival in children with leukemia and solid tumors. Members of the Surgical, Pathology and Radiation Therapy Divisions will actively participate in developing and conducting these studies. Collaboration with other Cooperative Groups will be achieved through the mechanism of Intergroup Studies.